The return of regular NFL referees won't put an end to hits that endanger players.

Case in point: Cleveland Browns wide receiver Joshua Cribbs was knocked out of Thursday's game after taking a blow to the head from Baltimore Ravens linebacker Dannell Ellerbe on a first-quarter punt return. Ellerbe sent Cribbs' helmet flying with a shoulder hit. Cribbs' head hit the turf as he fell.

To make matters worse for Cribbs, he was inadvertently kicked in the face by Ravens running back Anthony Allen, who was racing in to recover the fumble. Baltimore's Jameel McClain came up with the ball.

Cribbs lay on the ground for a few minutes before walking to the sideline. He then walked to the locker room with members of the Browns' training staff for evaluation.

Ellerbe was not penalized on the play. Analyst Mike Mayock noted on NFL Network's broadcast that Cribbs was not a defenseless player during the return.

Regular officials returned to the field Thursday night, less than 24 hours after they and NFL owners reached tentative agreement on a new contract to end a lockout of officials.